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Pasca
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« on: April 14, 2012, 07:43:36 19:43 »

Hi at all,
I want to build an Electromagnetic meter 0.1-3Ghz. I saw, in internet, a few units that have tri-axial sensors for isotropic measure, I'd like to know how this sensor is made.
I assumed, a one turn coil for axis in which measure the induced current (magnetic component) or a couple per axis small electrodes at a fixed distance for measuring the voltage picked up (electrical component). Is correct? there are more convenient solution? Which solutions have less realizzation problem? which is better?
I want to use 3 max2015 but if needed i can have 3 ad8313 for this pourpose.
I need help for this project and i want to share in this forum schematics, firmware and costrutive sensor solution.
Bye
Pasca
PS: I am italian, sorry for poor english (correct me!!!).
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Pasca
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« Reply #1 on: April 15, 2012, 02:55:10 14:55 »

Correction: Electromagnetic Field Meter
Is anyone interested?
The discussion is welcome!!!
Bye
Pasca
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enzine
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« Reply #2 on: April 15, 2012, 04:24:44 16:24 »

I would not discourage you, but if you want to do on the serious one , the subject is very complex. Embarrassed

The elementary antenna for measuring the electric field is the electrical dipole whose length must be very small compared to the wavelength that want to measure and then there are big problems of calibration.

Some theoretical references at:
http://it.wikipedia.org/wiki/Antenna_a_dipolo

and :

http://upload.wikimedia.org/wikipedia/commons/3/32/Frequency_selective_measurement_with_active_probes.pdf

There are also commercial products at low prices ($ 259.99):
http://www.amazon.com/gp/product/B001CNAPTU?ie=UTF8&tag=emw07-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B001CNAPTU

Hope that was helpful! Wink

Ciao
« Last Edit: April 15, 2012, 05:16:11 17:16 by enzine » Logged
Pasca
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« Reply #3 on: April 15, 2012, 05:53:47 17:53 »

Ok, Thank you for very interesting references.
Electrical dipole work only for narrow band measure, 3 biconic antennas could be adeguate eventually?
Calibration is not problem, i can use anecoic chamber with more instruments, I hope.
260 dollars hmmm, I am almost thinking to buy it.
Bye (Ciao)
Pasca
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enzine
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« Reply #4 on: April 15, 2012, 09:29:34 21:29 »

0.1-3Ghz


0.1-3Ghz = 0.1 GHz - 3GHz  or  0.1MHz-3GHz  or  ...?

Have a look at this  paper:

Wideband biconical antenna for accurate EMC measurements

http://eprints.uthm.edu.my/2065/1/Syarfa'_FKEE_(QIR2011).pdf

You're thinking of something similar?

Ciao
« Last Edit: April 15, 2012, 09:47:43 21:47 by enzine » Logged
Pasca
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« Reply #5 on: April 15, 2012, 11:00:02 23:00 »

Yes!!!
I also found this document: http://mwl.die.uniroma1.it/IACEm/11_misura_bandalarga.pdf
Now I have some documents to study.
Thanks Enzine.
Ciao
Pasca
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Pasca
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« Reply #6 on: April 23, 2012, 08:02:40 20:02 »

These are a few photos of commercial EMF Meter sensor.
Integrated circuit used is AD8312 (Q00).
Can someone explain me why short dipole has two resistor 316 ohm in the position that show in photo?
Thanks
Bye
Pasca
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enzine
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« Reply #7 on: April 23, 2012, 10:47:31 22:47 »

Very interesting question!

I think that the resistors were added to lower the overall figure of merit (Q) and for better impedance matching throughout the bandwidth of the antenna.
Something similar is used in the stripline and Vivaldi microwaves antennas.

At lower frequencies the use of resistors and inductors suitably positioned in the open dipoles antennas is at the basis of many experimental antennas used by radio amateurs.

The circuit may be fed to some EM simulator but should at least know the exact dimensions of the strips and,
 at least in my case,
should have a few years younger and a few neuron more...

Cheesy Cheesy Cheesy Cheesy Cheesy

Ciao!
« Last Edit: April 23, 2012, 10:54:54 22:54 by enzine » Logged
omni
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« Reply #8 on: April 23, 2012, 11:07:57 23:07 »

Here's a commercial EMF meter for 10MHz-8GHz (or so they claim): http://www.joyfay.com/us/electrosmog-rf-microwave-meter-up-to-8ghz-emf-tes593-jf02.html

Oh and a mandatory picture for these kinds of discussions (I love the coveralls, but I don't envy that job at all):
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